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Loft Conversion vs Extension: Which Adds More Value in Kent?

22 February 20268 min read


Loft Conversion vs Extension: Which Should You Choose?


Both routes are ones we build every week: loft conversions in Kent and house extensions in Kent, including loft conversions in Tunbridge Wells and the surrounding towns.


When your Kent home needs more space, two options dominate the conversation: converting the loft or building an extension. Both add valuable living space, but they serve different purposes, cost different amounts, and suit different properties.


This guide helps you decide which is the better investment for your situation.


Loft Conversions: Overview


A loft conversion transforms unused roof space into one or more habitable rooms. The most common types in Kent are:


Dormer Loft Conversion

The most popular type. A box-shaped structure is built out from the existing roof slope, creating full headroom and floor space.


Cost: £30,000 – £55,000

Space gained: 15–30m²

Timeline: 6–10 weeks


Hip-to-Gable Conversion

Common on semi-detached and detached homes. The sloped hip end of the roof is extended to a vertical gable wall, combined with a rear dormer.


Cost: £40,000 – £65,000

Space gained: 20–40m²

Timeline: 8–12 weeks


Mansard Conversion

The entire roof slope is rebuilt at a near-vertical angle with a flat roof on top. Creates maximum space but requires planning permission.


Cost: £45,000 – £75,000

Space gained: 25–45m²

Timeline: 10–14 weeks



Extensions: Overview


Extensions expand your home's footprint at ground level (or occasionally first floor). Common types include:


Single-Storey Rear Extension

The most popular option. Extends the kitchen or living area into the garden.


Cost: £25,000 – £70,000 (depending on size)

Space gained: 10–40m²

Timeline: 10–16 weeks


Double-Storey Extension

Adds space on two floors — typically kitchen/dining below and bedroom/bathroom above.


Cost: £50,000 – £120,000

Space gained: 20–80m²

Timeline: 14–24 weeks


Side Return Extension

Fills the narrow alley alongside a terraced or semi-detached house.


Cost: £20,000 – £45,000

Space gained: 5–15m²

Timeline: 8–12 weeks


Head-to-Head Comparison


Cost per m²

  • **Loft conversion:** £1,200–£2,000 per m²
  • **Extension:** £1,500–£2,500 per m²

    • Loft conversions typically offer better value per square metre because they use existing structure (the roof) rather than requiring new foundations.


    Value Added

  • **Loft conversion:** Adds 10–20% to property value
  • **Extension:** Adds 10–15% to property value

    • Loft conversions often add more proportional value because they create an additional bedroom — moving a 3-bed house to 4-bed is a significant upgrade in estate agent terms.


    Planning Permission

  • **Loft conversion:** Most dormer and hip-to-gable conversions fall under permitted development
  • **Extension:** Single-storey rear extensions usually fall under permitted development; larger projects may need planning

    • Disruption

  • **Loft conversion:** Less disruptive to daily life — work happens above your living areas. You can usually remain in the house throughout.
  • **Extension:** More disruptive — particularly kitchen extensions where the existing room is out of action during the build.

    • Which Properties Suit Each?

  • **Loft conversion:** Best for homes with good roof height (2.2m+ from joist to ridge), where additional bedrooms or a home office are the priority
  • **Extension:** Best for homes needing more ground-floor living space, open-plan kitchen-diners, or where the loft space is limited

    • Our Recommendation


    There's no one-size-fits-all answer, but here are general guidelines:


    Choose a loft conversion if:

  • You need an additional bedroom or two
  • Your ground-floor layout already works well
  • You want to maximise ROI on a moderate budget
  • You have adequate roof height

    • Choose an extension if:

  • You need a bigger kitchen or open-plan living space
  • Your loft has limited headroom or an awkward shape
  • You want to transform how you use your ground floor
  • You want seamless garden access

    • Consider both if:

  • You're planning a major renovation and want to maximise space and value simultaneously

    • Next Steps


    Whether you're leaning towards a loft conversion, an extension, or both, we can help. Book a free consultation to discuss your property and goals.


    We serve homeowners across Kent including Tunbridge Wells, Sevenoaks, and Tonbridge.


    View our completed building projects and customer reviews.


    Call 07850 357962 or request a free quote.


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